1. Field of the Invention
The present invention relates to a novel catalyst having a stable catalytic activity for catalyzing the reaction of an alcohol with carbon monoxide and oxygen to produce carbonic acid esters (i.e., carbonate) and also relates to a method of producing carbonic acid esters using the catalyst.
2. Prior Art
Carbonic acid esters, such as dimethyl carbonate and the like, have been used as a gasoline extender, an octane number improver, and organic solvents, and also recently used as raw materials instead of phosgene in the process of synthesizing isocyanates and polycarbonates, and various intermediates of agricultural chemicals and medicines.
In the producing carbonic acid esters by oxidation-carbonylation of an alcohol with carbon monoxide (CO) and oxygen (O.sub.2) in the presence of catalyst, a copper halide (copper (I)- or copper (II) halide) carried on carrier as a catalyst is known.
For example, International Application Publication WO 87/07601 discloses a process of producing carbonic acid esters by a vapor-phase reaction of an alcohol with carbon monoxide and oxygen in the presence of a catalyst comprising a metal halide or a mixed metal halide impregnated on a carrier, especially, copper (II) chloride, copper (II) chloride/potassium chloride and copper (II) chloride/magnesium chloride impregnated on activated carbon. In using one of these catalysts in the reaction of an alcohol with carbon monoxide and oxygen, however, the conversion of an alcohol and the selectivity to carbonic acid esters are unsatisfactory and a large amount of by-product is yielded. For example, methyl chloride is formed during an initial stage of the reaction and causes metal to corrode. Therefore the conventional catalytic system requires a highly expensive corrosion-resisting reactor vessel.